Bilateral total knee arthroplasties were performed in 26 patients with severe rheumatoid arthritis and osteoarthritis. Twelve had simultaneous operations bilaterally and 14 had separate, staged procedures. The improvement in the 2 groups of patients was statistically comparable to the relief of pain and the over-all restoration of function. There were no intraoperative complications. The postoperative morbidity was minimum and was not predominant in either group.